Incorporation of boron into metakaolin-based geopolymers for radionuclide immobilisation and neutron capture potential

Niu, X.*; Elakneswaran, Y.*; Li, A.*; Seralathan, S.*; Kikuchi, Ryosuke*; Hiraki, Yoshihisa; Sato, Junya; Osugi, Takeshi; Walkley, B.*

Cement and Concrete Research, 190, p.107814_1 - 107814_17, 2025/04

https://doi.org/10.1016/j.cemconres.2025.107814

Background aerial monitoring and UAV radiation monitoring technology development for emergency response and preparedness in fiscal year 2023 (Contract research)

Futemma, Akira; Sanada, Yukihisa; Nakama, Shigeo; Sasaki, Miyuki; Ochi, Kotaro; Sawahata, Yoshiro*; Kawasaki, Yoshiharu*; Iwai, Takeyuki*; Hiraga, Shogo*; Haginoya, Masashi*; et al.

JAEA-Technology 2024-022, 170 Pages, 2025/03

JAEA-Technology-2024-022.pdf:15.09MB

On March 11, 2011, the 2011 off the Pacific coast of Tohoku Earthquake caused a tsunami that led to the Fukushima Daiichi Nuclear Power Station accident, releasing radioactive material into the environment. Since then, Aerial Radiation Monitoring (ARM) using manned helicopters has been employed to measure radiation distribution. As a commissioned project from the Nuclear Regulation Authority, the Japan Atomic Energy Agency (JAEA) utilizes this technology for emergency monitoring during nuclear facility accidents, aiming to provide prompt results by pre-arranging information on background radiation, topography, and control airspaces around nuclear power plants nationwide. In fiscal year 2023, the commissioned project included conducting ARM around the Sendai Nuclear Power Station and preparing related information. To enhance effectiveness during emergencies, ARM and the first domestic training flight of Unmanned Aerial Vehicles (UAVs) were conducted during the FY2023 Nuclear Energy Disaster Prevention Drill. Furthermore, UAVs radiation monitoring technology was advanced by selecting UAVs and investigating their performance. This report summarizes the results and technical issues identified providing insights to improve emergency preparedness.

Robustness of ferromagnetism in van der Waals magnet FeGeTe to hydrostatic pressure

Wang, Y.*; Zeng, X.-T.*; Li, B.*; Su, C.*; Hattori, Takanori; Sheng, X.-L.*; Jin, W.*

Chinese Physics B, 34(4), p.046203_1 - 046203_6, 2025/03

https://doi.org/10.1088/1674-1056/adb26f

Two-dimensional van der Waals ferromagnet FeGeTe (FGT) holds a great potential for applications in spintronic devices, due to its high Curie temperature, easy tunability, and excellent structural stability in air. In this study, we have performed high-pressure neutron powder diffraction (NPD) up to 5 GPa, to investigate the evolution of its structural and magnetic properties with hydrostatic pressure. The NPD data clearly reveal the robustness of the ferromagnetism in FGT, despite of an apparent suppression by hydrostatic pressure. As the pressure increases from 0 to 5 GPa, the Curie temperature is found to decrease monotonically from 225(5) K to 175(5) K, together with a dramatically suppressed ordered moment of Fe, which is well supported by the first-principles calculations. Although no pressure-driven structural phase transition is observed up to 5 GPa, quantitative analysis on the changes of bond lengths and bond angles indicate a significant modification of the exchange interactions, which accounts for the pressure-induced suppression of the ferromagnetism in FGT.

Development of on-site detection system for concealed nuclear materials

Tanabe, Kosuke*; Komeda, Masao; Toh, Yosuke; Kitamura, Yasunori*; Misawa, Tsuyoshi*

Nihon Genshiryoku Gakkai-Shi ATOMO, 67(3), p.198 - 202, 2025/03

https://doi.org/10.3327/jaesjb.67.3_198

no abstracts in English

Integrity evaluation of boundary function of main components in nuclear plants during severe accidents

Tsukimori, Kazuyuki; Yada, Hiroki

Journal of Pressure Vessel Technology, 147, p.031901_1 - 031901_9, 2025/00

https://doi.org/10.1115/1.4067760

After the accident at the Fukushima Daiichi Nuclear Power Plant, very strict safety measures were implemented for nuclear power plants in Japan. It thus becomes a crucial issue if the safety of a plant is maintained or not at beyond design basis events. In this study, head plates and bellows were examined as components that compose the parts of the boundary of vessels that contain the primary coolant of a prototype fast breeder reactor. The behaviors of buckling, post-buckling deformation, and penetration failure, that is, loss of boundary function of these components with increasing pressure were investigated. The series of this research program started in FY2013 and the research proceeded step by step. The new result in this paper is the application of the proposed criteria to head plates and bellows, and a conservative estimation of penetration failure of these components is obtained.

Application of indentation technique to material degradation evaluation in the mercury target vessel for spallation neutron sources

Wakui, Takashi; Saito, Shigeru; Futakawa, Masatoshi

Jikken Rikigaku, 24(4), p.212 - 218, 2024/12

Irradiation damage is one of the main factors determining the lifetime of the mercury target vessel for spallation neutron source in J-PARC. To understand material degradation of the used vessels, it is planned to conduct an evaluation using inverse analyses with indentation tests on the structural materials of the used vessels and numerical experiments. This evaluation technique was applied to two kinds of ion-irradiated materials with different displacement damage doses, in which the irradiation condition was simulated. It could be confirmed that the ultimate strength increased, and the total elongation decreased with increasing irradiation. These trends are like the material degradation behaviors which have been reported by using small specimen's tensile tests.

Reports on research activities and evaluation of advanced computational science in FY2023

Center for Computational Science & e-Systems

JAEA-Evaluation 2024-001, 40 Pages, 2024/10

JAEA-Evaluation-2024-001.pdf:1.46MB

Research on advanced computational science for nuclear applications, based on "the plan to achieve the medium- and long-term goal of the Japan Atomic Energy Agency", has been performed by Center for Computational Science & e-Systems (CCSE), Japan Atomic Energy Agency. CCSE established a committee consisting of external experts and authorities which evaluates and advises toward the future research and development. This report summarizes the results of the R&D performed by CCSE in FY2023 (April 1st, 2023 - March 31st, 2024) and their evaluation by the committee.

Biofilm-mediated interactions between plastics and radiocesium in coastal environments

Battulga, B.; Nakanishi, Takahiro; Atarashi-Andoh, Mariko; Otosaka, Shigeyoshi*; Koarashi, Jun

Environmental Science and Pollution Research, 31, p.60080 - 60092, 2024/10

https://doi.org/10.1007/s11356-024-35164-y

A ubiquitous distribution of plastic debris has been reported in aquatic and terrestrial environments; however, the interactions between plastics and radionuclides and the radioactivity of environmental plastics remain largely unknown. Here, we characterize biofilms developing on the surface of plastic debris to explore the role of plastic-associated biofilms as an interaction medium between plastics and radiocesium (Cs) in the environment. Biofilm samples were extracted from plastics (1-50 mm in size) collected from two contrasting coastal areas in Japan. The radioactivity of plastics was estimated based on the Cs activity concentration of the biofilms and compared seasonally with surrounding environmental samples (i.e., sediment and sand). Cs traces were detected in biofilms with activity concentrations of 21-1300 Bq kg biofilm (dry weight), corresponding to 0.04-4.5 Bq kg plastic (dry weight). Our results reveal the interaction between Cs and plastics and provide evidence that organic and mineral components in biofilms are essential in Cs retention in environmental plastics.

Development of nanosized graphene material for neutron intensity enhancement below cold neutron energy

Teshigawara, Makoto; Ikeda, Yujiro*; Muramatsu, Kazuo*; Sutani, Koichi*; Fukuzumi, Masafumi*; Noda, Yohei*; Koizumi, Satoshi*; Saruta, Koichi; Otake, Yoshie*

Journal of Neutron Research, 26(2-3), p.69 - 74, 2024/09

https://doi.org/10.3233/JNR-240002

Slow neutrons, such as cold neutrons, are important non-destructive probes not only for basic physics but also for the structural genomics advancements in the life sciences and the battery technology advancements needed for the transition to a hydrogen society. Neutron-based science is also known as high-neutron-intensity-dependent science. A new unique method focusing on nanosized particle aggregation has been proposed to increase neutron intensity in that energy region. The method is based on intensity enhancement by multiple coherent scatterings with nanosized particle aggregation. The aggregation of nanosized particles matches the wavelength of below cold neutrons, causing a similar effect to coherent scattering, so-called Bragg scattering, leading to neutron intensity enhancement by several orders of magnitude. Nanodiamonds and magnesium hydride have recently been studied numerically and experimentally. The major challenge with nanodiamonds in practical applications is the molding method. Another carbon structure, graphene is focused on to find a solution to this problem. It is hypothesized that nanosized graphene could aid coherent neutron scattering under particle size conditions similar to nanodiamonds. We report the potential of nanosized graphene as a reflector material below cold neutrons, together with experimental results.

Uncertainty reduction of the FPs transport mechanism and debris degradation behavior and evaluation of the reactor contamination of debris state on the basis of the accident progression scenario of Fukushima Daiichi Nuclear Power Station Unit 2 and 3 (Contract research); FY2022 Nuclear Energy Science & Technology and Human Resource Development Project

Collaborative Laboratories for Advanced Decommissioning Science; Tokyo Institute of Technology*

JAEA-Review 2024-010, 112 Pages, 2024/08

JAEA-Review-2024-010.pdf:6.49MB

The Collaborative Laboratories for Advanced Decommissioning Science (CLADS), Japan Atomic Energy Agency (JAEA), had been conducting the Nuclear Energy Science & Technology and Human Resource Development Project (hereafter referred to "the Project") in FY2022. The Project aims to contribute to solving problems in the nuclear energy field represented by the decommissioning of the Fukushima Daiichi Nuclear Power Station, Tokyo Electric Power Company Holdings, Inc. (TEPCO). For this purpose, intelligence was collected from all over the world, and basic research and human resource development were promoted by closely integrating/collaborating knowledge and experiences in various fields beyond the barrier of conventional organizations and research fields. The sponsor of the Project was moved from the Ministry of Education, Culture, Sports, Science and Technology to JAEA since the newly adopted proposals in FY2018. On this occasion, JAEA constructed a new research system where JAEA-academia collaboration is reinforced and medium-to-long term research/development and human resource development contributing to the decommissioning are stably and consecutively implemented. Among the adopted proposals in FY2021, this report summarizes the research results of the "Uncertainty reduction of the FPs transport mechanism and debris degradation behavior and evaluation of the reactor contamination of debris state on the basis of the accident progression scenario of Fukushima Daiichi Nuclear Power Station Unit 2 and 3" conducted in FY2022. The present study aims to elucidate the cause of the high dosage under shield plug by clarification of to the cesium behavior of migration, adhesion to structure and deposition as well as evaluate the properties of metal-rich debris predeceasing melted through the materials science approach based on the most probable scenario of accident progression of Unit 2 and 3. In this fiscal year, the followings were achieved.